Distance from armor deck to top edge of the barbettes.

[hans zurbriggen]

Hello Mr. Nilsson,
thanks again for correcting me. In Gally's drawing, I interpreted 15850 as total height of hull (from lower edge of keel to upper edge of Oberdeck at center ship transversely, at A turret level). This is not so clear from drawing, where the double line only represent the height at 'mitte schiff' (center ship) and at 'seite schiff' (ship side) different due to canter (see below).

hull.jpg (30.45 KiB) Viewed 1801 times

However, if you are sure that 15850 is from lower edge of Oberdeck, I do not fully understand your calculation yet: based on what you say, clearance ('void' space?) between decks should be 15850-10300-100 = 5450 (why do you say +100 if both measures are lower edge of both decks?).
From ballistic viewpoint, I think however relevant distance (theoretically) should be 15850-10300-100+50 = 5500, as it's upper edge of Oberdeck that initiate shell fuze even ignoring the teak thickness of the deck.

hans

[Herr Nilsson]

Gally's drawing is copied from the lines drawing plan. A lines drawing is always without plating.

My calculation is the distance between the upper edge of the Panzerdeck and the lower edge of the Oberdeck:

Lower edge Panzerdeck + armor thickness = upper edge Panzerdeck
->
Lower edge Oberdeck - upper edge Panzerdeck = distance.

[hans zurbriggen]

Hello Mr. Nilsson,
thanks for this explanation about lines drawing: does this mean 15850 does not include keel plating too? What about 10300?

Regarding calculation itself you have written: '15,850 mm is lower edge of the Oberdeck and 10,300 is lower edge of the Panzerdeck'. To get the distance between the two decks armor thickness (100) should be subtracted, not added.
The final result for distance between upper edge of Panzerdeck and lower edge of Oberdeck should be 15850 - 10300 - 100 = 5450 and not 5650.
Do you agree ?

hans

[Herr Nilsson]

Yes.
Yes.
No.

[hans zurbriggen]

Hello Mr. Nilsson,
thanks for the first 2 answers: clear now to me how to read drawing.

I do not understand your last answer: can you please tell me what is the final result for distance between the two armor decks ?
5450 (as per my calculation) or 5650 (as per your calculation).
If you use lower edges for both decks, armor thickness should be subtracted not added.
Using my result starting from keel we have 10300 (up to lower edge Panzerdeck) + 100 (armor thickness) + 5450 (distance to lower edge Oberdeck) = 15850 (total height) as per drawing. I think you are getting a wrong result.

hans

[Herr Nilsson]

Yes, my error in reasoning. You‘re right.

[hans zurbriggen]

Hello Mr. Nilsson,
thanks a lot for your precious help.

hans

[José M. Rico]

Summarizing, the maximum distance at nominal values from the lower edge of the keel (Unterkante Kiel) to the top of the roof of Turret Anton at frame 192,55 is calculated as follows:

22 mm (keel plate) +
10,300 mm (from upper edge of keel plate to lower edge of Panzerdeck) +
6,390 mm (from lower edge of Panzerdeck to upper edge of barbette) +
70 mm (space between barbette and turret) +
3,500 mm (turret height according to Jack Brower Bismarck Anatomy book) =
____________
20,282 mm

[Bill Jurens]

If I might extend this a bit, I'd like a bit more feedback -- if anyone has any -- regarding the very slight taper of the barbettes.

I can't see how the introduction of this very small taper -- which would have greatly complicated manufacture -- could have had any significant effect structurally, and so assume that it represented a weight-saving strategy, i.e. an attempt to save weight by accommodating a somewhat larger requirement for space near the bottom to a somewhat smaller turret. Reducing turret width might decrease overall turret weight by (perhaps) 50 tons or so, and the imposition of a taper would not make a great difference in weight (perhaps 20 tons) and center of gravity, but cumulatively the saving over four turrets -- let's say as a rough estimate of 250 tons or so might have seen to have been worth it in spite of the extra effort involved in manufacture. Alternatively, there might have been some feeling that the plates of the barbettes somehow interlocked more rigidly in a slightly tapered configuration, but the taper is so small as to appear to be essentially negligible. And the weight saving of (say) 20 tons per barbette alone, i.e. about 80 tons in total would not seem to be overall worthwhile.

Another question, if the taper were introduced to accommodate a slightly smaller-than-expected turret, revolves around why such a scheme might have been used on Scharnhorst as well. I haven't checked my Sharnhorst drawings on this, but there may be one or more hidden clues there.

At any rate, comments very welcome indeed.

Bill Jurens

[hans zurbriggen]

Hello Mr Jurens,
very interesting question. Curiously, from my drawings, it looks like SH's barbette were more sloped than BS's and that 'H' class' were approximately cylindrical. Can anyone confirm ?
Weight of the whole turret insists on revolving ring (inside barbette) that looks vertical ('cilindrical' until Batteriedeck, when outer shape becomes ottagonal until Mittleres Platform level). Then it is sharply bent outward until hull bottom that is met at 'longitudinal frame' III (this is one of the weight supporting 'longitudinal frames' when in dry dock). This (bad quality copy from same Bunderarchiv drawing dated 1936) possibly can mean something to a naval architect (it refers to 'C' turret). Conical barbette shape is hardly appreciable, but is there. I have added longitudinal frames numbers.

C_turret.jpg (88.53 KiB) Viewed 1693 times

hans

[Bill Jurens]

A plausible hypothesis regarding barbette taper (??)

It is fairly well accepted that Sharnhorst/Gneisenau were designed so that it would be possible to up-gun them from c.28 cm to 38cm after completion. In that regard, it might have been a good idea to install lower turret structures to handle the larger guns when the ships were constructed and, in the interim, fit guns which were in effect 'too small' above them. In order to cut down weight and avoid a geometrically offensive 'shelf' around the smaller gunhouse, at the top, rather than install a cylindrical barbette, one would then place a tapered barbette, suited -- in this case -- for 38cm guns at the bottom and 28 cm guns at the top. This is geometrically somewhat cumbersome, and would require replacing or modifying the barbette armor itself when upgunning was done, but might have been seen to have been preferable to placing in a 28cm cylindrical barbette in the first place, which might have visually revealed what were probably secret intentions when the ships entered service. The taper is so small that it's virtually undetectable to casual -- and perhaps even careful -- foreign observers.

I haven't looked into this in detail, but if correct, I would not be surprised if a similar strategy was employed in the construction of Bismarck and Tirpitz as well, i.e. fitting a tapered barbette which would accommodate a larger-caliber gun system below, but tapering it to fit a nominally 'undersized' turret structure up above.

Comments, as always, welcome...

Bill Jurens

[Herr Nilsson]

There were conical barbettes also on Derfflinger. I have the dim feeling it might have to do with the supporting structures/bulkheads below the armor deck and/or transformation of the gun-support „cylinder“ from an octagonal shape to a circle.

[hans zurbriggen]

Hello Mr. Jurens, hello Mr. Nilsson,
I had same feeling as Mr. Nilsson, but I can't see any logical reason for truncated cone barbettes in relation to revolving ring 'cylindrical' structure. I tend to agree with Mr.Jurens that attributes truncated cone shape to the 'smaller than planned' turrets.

hans